Non-Patent Literature 1 (Nick McKeown et al., “Open Flow: Enabling Innovation in Campus Networks”, ACM SIGCOMM Computer Communication Review, Vol. 38, No. 2, 2008. (http://www.openflowswitch.org//documents/openflow-wp-latest.pdf)) describes a technique called “Open Flow”. In the Open Flow, route control, failure recovery, load distribution and optimization are performed on an individual flow basis. In the Open Flow, an open flow switch serving as a forwarding node and an open flow controller controlling the open flow switch are used.
The open flow switch is provided with a flow table that indicates a correspondence relationship between a “match condition” and an “action”, and operates in accordance with the flow table. More specifically, when receiving a packet, the open flow switch refers to the flow table to search the flow table for an entry that matches the received packet. If an entry matching the received packet is registered on the flow table, the open flow switch executes processing designated by the action of the matching entry on the received packet. Typically, the open flow switch forwards the received packet to an output port designated by the action.
It is the open flow controller that controls the flow table of the open flow switch. That is, the open flow controller instructs the open flow switch to carry out such processing as new entry addition, entry change and entry deletion and thereby controls an operation of the open flow switch For example, if there is no matching entry in the flow table, the open flow switch requests the open flow controller for route setting. In response to the route setting request, the open flow controller designs a route of a flow of the received packet. Then, the open flow controller instructs each switch on the designed route to add a new entry such that packet forwarding along the designed route is achieved.